Surface energy modification for wetting substances

ABSTRACT

A container comprising a finish, a sidewall portion extending from the finish, a base portion extending from the sidewall portion and enclosing the sidewall portion to form a volume therein for retaining a commodity, and a coating disposed along at least a portion of the finish, the sidewall portion, or the base portion for providing a low-energy surface for improved dispensing of the commodity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/350,541, filed on Jun. 2, 2010. The entire disclosure of the above application is incorporated herein by reference.

FIELD

This disclosure generally relates to containers for retaining a commodity, such as a solid or liquid commodity. More specifically, this disclosure relates to a container having a low energy coating applied to at least an interior thereof for facilitating extraction of the commodity.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

As a result of environmental and other concerns, plastic containers, more specifically polyester and even more specifically polyethylene terephthalate (PET) containers are now being used more than ever to package numerous commodities previously supplied in glass containers. Manufacturers and fillers, as well as consumers, have recognized that PET containers are lightweight, inexpensive, recyclable and manufacturable in large quantities.

Blow-molded plastic containers have become commonplace in packaging numerous commodities. PET is a crystallizable polymer, meaning that it is available in an amorphous form or a semi-crystalline form. The ability of a PET container to maintain its material integrity relates to the percentage of the PET container in crystalline form, also known as the “crystallinity” of the PET container. The following equation defines the percentage of crystallinity as a volume fraction:

${\% \mspace{14mu} {Crystallinity}} = {\left( \frac{\rho - \rho_{a}}{\rho_{c} - \rho_{a}} \right) \times 100}$

where ρ is the density of the PET material; ρa is the density of pure amorphous PET material (1.333 g/cc); and ρc is the density of pure crystalline material (1.455 g/cc).

Container manufacturers use mechanical processing and thermal processing to increase the PET polymer crystallinity of a container. Mechanical processing involves orienting the amorphous material to achieve strain hardening. This processing commonly involves stretching an injection molded PET preform along a longitudinal axis and expanding the PET preform along a transverse or radial axis to form a PET container. The combination promotes what manufacturers define as biaxial orientation of the molecular structure in the container. Manufacturers of PET containers currently use mechanical processing to produce PET containers having approximately 20% crystallinity in the container's sidewall.

Thermal processing involves heating the material (either amorphous or semi-crystalline) to promote crystal growth. On amorphous material, thermal processing of PET material results in a spherulitic morphology that interferes with the transmission of light. In other words, the resulting crystalline material is opaque, and thus, generally undesirable. Used after mechanical processing, however, thermal processing results in higher crystallinity and excellent clarity for those portions of the container having biaxial molecular orientation. The thermal processing of an oriented PET container, which is known as heat setting, typically includes blow molding a PET preform against a mold heated to a temperature of approximately 250° F.-350° F. (approximately 121° C.-177° C.), and holding the blown container against the heated mold for approximately two (2) to five (5) seconds. Manufacturers of PET juice bottles, which must be hot-filled at approximately 185° F. (85° C.), currently use heat setting to produce PET bottles having an overall crystallinity in the range of approximately 25%-35%.

Unfortunately, with some commodities, such as mayonnaise, it has been found that the commodity has a tendency to adhere to the internal sides of containers preventing complete usage thereof. Specifically, mayonnaise is a highly viscous emulsion made with mostly oil, water and at least egg whites. This emulsion adheres to many surfaces, such as glass, plastic, and the like. In the past, it was necessary to use a knife or other implement to remove the commodity from the internal sides. With the recent move to plastic squeezable containers, it has been found that the commodity or product still adheres to the sidewalls. Although some plastic materials may help minimize this effect, these materials, such as PP, are not recyclable, unlike PET containers.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

According to the principles of the present teachings, a container is provided having a low energy coating applied to at least an interior thereof for facilitating extraction of the commodity.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1A is a side view of an exemplary container incorporating the features of the present teachings; and

FIG. 1B is an enlarged cross-sectional view of the container of FIG. 1A illustrating exemplary coating layers.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

This disclosure provides for a container being made of PET and incorporating a coating system that modifies the internal surface energy of the container to facilitate removal for a commodity, such as mayonnaise. According to these principles, the PET container provides improved wetting properties, while maintaining recyclability.

It should be appreciated that the size and specific configuration of the container may not be particularly limiting and, thus, the principles of the present teachings can be applicable to a wide variety of PET container shapes. Therefore, it should be recognized that variations can exist in the present embodiments. That is, it should be appreciated that the teachings of the present disclosure can be used in a wide variety of containers, including reusable/disposable packages including resealable plastic bags (e.g., ZipLock® bags), resealable containers (e.g., TupperWare® containers), dried food containers (e.g., dried milk), drug containers, chemical packaging, squeezable containers, recyclable containers, and the like.

Accordingly, the present teachings provide a plastic, e.g. polyethylene terephthalate (PET), container generally indicated at 10. The exemplary container 10 can be substantially elongated when viewed from a side. Those of ordinary skill in the art would appreciate that the following teachings of the present disclosure are applicable to other containers, such as rectangular, triangular, pentagonal, hexagonal, octagonal, polygonal, or square shaped containers, which may have different dimensions and volume capacities. It is also contemplated that other modifications can be made depending on the specific application and environmental requirements.

In some embodiments, container 10 has been designed to retain a commodity. The commodity may be in any form such as a solid or semi-solid product. In one example, a commodity may be introduced into the container during a thermal process, typically a hot-fill process. For hot-fill bottling applications, bottlers generally fill the container 10 with a product at an elevated temperature between approximately 155° F. to 205° F. (approximately 68° C. to 96° C.) and seal the container 10 with a closure before cooling. In addition, the plastic container 10 may be suitable for other high-temperature pasteurization or retort filling processes or other thermal processes as well. In another example, the commodity may be introduced into the container under ambient temperatures.

As shown in FIG. 1, the exemplary plastic container 10 according to the present teachings defines a body 12, and includes an upper portion 14 having a cylindrical sidewall 18 forming a finish 20. Integrally formed with the finish 20 and extending downward therefrom is a shoulder portion 22. The shoulder portion 22 merges into and provides a transition between the finish 20 and a sidewall portion 24. The sidewall portion 24 extends downward from the shoulder portion 22 to a base portion 28 having a base 30. In some embodiments, sidewall portion 24 can extend down and nearly abut base 30, thereby minimizing the overall area of base portion 28 such that there is not a discernable base portion 28 when exemplary container 10 is uprightly-placed on a surface.

The exemplary container 10 may also have a neck 23. The neck 23 may have an extremely short height, that is, becoming a short extension from the finish 20, or an elongated height, extending between the finish 20 and the shoulder portion 22. The upper portion 14 can define an opening for filling and dispensing of a commodity stored therein. Although the container is shown as a wide-mouth mayonnaise container, it should be appreciated that containers having different shapes, such as sidewalls and openings, can be made according to the principles of the present teachings.

The finish 20 of the exemplary plastic container 10 may include a threaded region 46 having threads 48, a lower sealing ridge 50, and a support ring 51. The threaded region provides a means for attachment of a similarly threaded closure or cap (not shown). Alternatives may include other suitable devices that engage the finish 20 of the exemplary plastic container 10, such as a press-fit or snap-fit cap for example. Accordingly, the closure or cap engages the finish 20 to preferably provide a hermetical seal of the exemplary plastic container 10. The closure or cap is preferably of a plastic or metal material conventional to the closure industry and suitable for subsequent thermal processing.

In an effort to improve the dispensing of some commodities, such as mayonnaise, container 10 can further comprise an internal coating 60 applied to at least an internal sidewall of container 10. It should be appreciated that the coating 60 can be applied to other surfaces of container 10, including external surfaces, if desired and the teachings of the present application should not be considered limited to only internal uses.

With particular reference to FIG. 1B, container 10 can comprise internal coating 60 applied to at least an internal surface of base 30, sidewall portion 24, shoulder portion 22, finish 20, and combinations thereof. In some embodiments, coating 60 can comprise a first layer 62, a second layer 64, and a third layer 66. In some embodiments, first layer 62 can be a low-energy coating. That is, the surface of PET is traditionally at a high-energy level. Therefore, application of a first layer in contact with the PET should be a low-energy level for adherence to the high-energy level PET material. To this end, first layer 62 can be applied as a gas, such as hexamethyldisilazane. Application of first layer 62 thereby creates a bonding layer for application of additional layers.

In some embodiments, second layer 64 can be a high-energy coating for adherence to the low-energy level of first layer 62. To this end, second layer 64 can be applied as a gas, such as hexamethyldisiloxane. Application of second layer 64 thereby creates a layer having a high-energy level approach that of glass. The high-energy level of second layer 64 thus adheres to the low-energy layer 62. The combination of first layer 62 and second layer 64 can provide a barrier function to inhibit or at least minimize transmission of oxygen or carbon dioxide into container 10.

Still further, third layer 66 can be a low-energy coating for adherence to the high-energy level of second layer 64. To this end, third layer 66 can be applied as a gas, such as hexamethyldisilazane. Application of third layer 66 thereby creates a final low-energy coating and contact area layer for the commodity or product. That is, the commodity contained in container 10 would be in contact with third layer 66. The low-energy properties of third layer 66 provide a beading response and tailored surface energy modification for improved dispensing of the commodity.

It should be appreciated that coating 60 can comprise other layer arrangements. By way of non-limiting example, in some embodiments, first layer 62 and/or second layer 64 can be eliminated if the adherence of third layer 66 to sidewall portion 24 is sufficient for the intended use and commodity and the need for a barrier function, which is provided by the combination of first layer 62 and second layer 64, is unnecessary. Therefore, in such embodiment, coating 60 would comprise only a single layer (i.e. third layer 66).

It should further be appreciated that container 10, with coating 60, is sufficient to provide both improved product dispensing and/or removal, while maintaining it recyclability.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention. 

1. A container comprising: a finish; a sidewall portion extending from said finish; a base portion extending from said sidewall portion and enclosing said sidewall portion to form a volume therein for retaining a commodity; a coating disposed along at least a portion of said finish, said sidewall portion, or said base portion for providing a low-energy surface for improved dispensing of the commodity.
 2. The container according to claim 1 wherein said coating is disposed within said volume.
 3. The container according to claim 1 wherein said coating comprises a first layer.
 4. The container according to claim 3 wherein said first layer is made of hexamethyldisilazane.
 5. The container according to claim 1 wherein said coating comprises: a first layer; a second layer adhered to said first layer; and a third layer adhered to said second layer.
 6. The container according to claim 5 wherein said first layer is made of hexamethyldisilazane, said second layer is made of hexamethyldisiloxane, and said third layer is made of hexamethyldisilazane.
 7. The container according to claim 1 wherein said coating is made of a recyclable material.
 8. A container comprising: a finish; a sidewall portion extending from said finish; a base portion extending from said sidewall portion and enclosing said sidewall portion to form a volume therein for retaining a commodity; a multi-layer coating disposed along at least a portion of said finish, said sidewall portion, or said base portion for providing a low-energy surface for improved dispensing of the commodity.
 9. The container according to claim 8 wherein at least one of the layers of said multi-layer coating comprises hexamethyldisilazane.
 10. The container according to claim 8 wherein said multi-layer coating comprises hexamethyldisilazane and hexamethyldisiloxane.
 11. The container according to claim 8 wherein said multi-layer coating is made of recyclable material.
 12. A container comprising: a finish; a sidewall portion extending from said finish; a base portion extending from said sidewall portion and enclosing said sidewall portion to form a volume therein for retaining a commodity; a coating disposed along said sidewall portion and said base portion for providing a low-energy surface for improved dispensing of the commodity.
 13. The container according to claim 12 wherein said coating is a multi-layer coating.
 14. The container according to claim 12 wherein said coating comprises hexamethyldisilazane.
 15. The container according to claim 12 wherein said coating comprises hexamethyldisilazane and hexamethyldisiloxane.
 16. The container according to claim 12 wherein said coating is made of recyclable material. 